Display technologies based on the directed movement or rotation of particles suspended in a fluid medium are currently being developed to store and retrieve information. Such displays may find use in computer displays, PDA's, electronic signs, and electronic books.
One such technology, called gyricon displays, but also known by other names such as electrical twisting-ball displays or rotary ball displays, see U.S. Pat. Nos. 4,126,854 and 4,143,103 the contents of which are incorporated herein by reference in their entirety, were first developed over twenty years ago. In a gyricon display bichromal balls or cylinders, which are electrically anisotropic, may be suspended in a dielectric medium between addressable electrodes on surfaces making up the display housing. The balls or cylinders are electrically dipolar in the presence of the fluid and so are subject to rotation upon application of an electric field, as by matrix-addressable electrodes. The electrode closest to the viewing surface of the display is preferably transparent. An observer viewing the display sees an image formed by the black and white pattern of the balls or cylinders as rotated by the matrix-addressable electrodes to expose their black or white faces to the viewing surface.
Besides gyricon technology, other display technologies utilizing suspended particles in a fluid medium include: rod-shaped or plate-like colloidal particles that are suspended in a fluid and which become aligned thereby permitting the formation of images by restriction or passage of light upon application of an external electric field; and charged micro-particle suspended in a dielectric fluid which are electrophoretic and move to create an image upon application of an external electric field.
Gyricon displays in particular have numerous advantages over conventional electrically addressable visual displays, such as LCD and CRT displays. They are suitable for viewing in ambient light and retain an image indefinitely in the absence of an applied electric field which reduces power consumption by the display and is an important advantage for this technology in portable display applications. Gyricon displays may also be made lightweight, flexible, foldable, and with many other familiar and useful characteristics of ordinary writing paper. Thus, at least in principle, they are suitable both for display applications and for so-called electric paper or interactive paper applications, in which they serve as an electrically addressable, reusable (and thus environmentally friendly) substitute for ordinary paper. For further advantages of the gyricon display, see U.S. Pat. No. 5,389,945, the contents of which are incorporated herein by reference in their entirety.
In the fabrication of display devices utilizing suspended particles in a fluid display medium, for example point of purchase displays which are designed to contain the display medium in an enclosure, it is important to maintain a specified fluid level in the display and to exclude gases like air from the display housing system. In the course of fabrication of these devices, there is a certain amount of air that is trapped in the system. It is important to remove this air so that there is intimate contact between the housing packaging elements and or electrodes of the display, and the display medium. Furthermore, in order to maintain the proper fluid level in the package, it is important that the fabricator of the display be able to temporarily breach the package to remove air, remove excess fluid, or to add fluid to the package without compromising the integrity of the sealed display package.
One method of accomplishing the above objective is to provide a means of ingress into the package and attach a valve at the other end. However, such devices are bulky and expensive to produce in the miniature sizes desired for display use. Another approach to this problem is to incorporate small-bore tubing in the package where the tubes could be pinched shut after use. This approach suffers from the problem of continuing leakage from the tubes. Thus a reliable means of temporarily breaching the package seal is required while maintaining seal integrity. The sealing system must be small enough to fit within the housing constraints specified for these devices.